Roof drilling in mines is a common procedure to provide holes for roof bolts which penetrate the overhead material in a mine and reinforce it against collapse. A full discussion of the use of roof drilling and roof bolts is found in a U.S. Pat. No. 4,226,290 issued to L. H. McSweeney on Oct. 7, 1980. Other United States patents directed to the same problem in mining are those issued to Liebee, U.S. Pat. No. 3,519,091, on July 7, 1970 and to Jamison, U.S. Pat. No. 4,454,922, on June 19, 1984.
All of the above patents are directed to means for holding and driving the rotating roof drill bits and also the connecting steels, that is, the elongate shafts which must be added as the hole progresses into the mine roof. The low overhead available requires, often, that the driving shafts be added as the hole gets deeper into the material being drilled. This elongate assembly or drill rod must be attached in such a way that the power drive can be efficiently transmitted to the bit and also in such a way that the driving steels can be removed once the hole has reached the proper depth. Another requirement of the bit drive is that it be hollow so that fluid or vacuum air above or below atmospheric pressure can be transmitted to remove the tailings and cool the bit.
The Liebee patent above identified discloses the use of hexagonal drive members and connections with frictional engagement from one member to the other. The Jamison patent discloses the use of helical interfitting members and sockets to effect the drive and restrain separation during removal of the assembled drill steels from the bore. The above-identified McSweeney patent discloses two connecting and retention systems. The first includes a drive socket with a separate cap which receives a drive end in one circumferential orientation and prevents withdrawal in a second circumferential orientation. The second retention system involves a groove in an inner telescoping part registering with a hole in an outer telescoping part so that a retention pin or wire can be driven into the groove through the hole to lock the parts against axial withdrawal.
It is an object of the present invention to provide an interlock system which will effectively drive the bit and drill steels in either direction and at the same time prevent axial separation of the bit and the various elements of the drive steel assembly, thus providing a system which affords effective protection for the operator when retracting the drill steel from each hole on an axial plane.
It is a further object to provide a roof bit drive rod assembly which involves only two parts for each drive chuck and each joint with no need for pins or wires or frictional elements and yet which provides a positive drive and axial interlock.
It is a further object to provide an interlock system which requires no special tools for assembly or disassembly and which can be readily assembled or disassembled.
A still further object is the provision of a drill steel and chuck system which will accept all existing conventional starters and drivers now in use.
It is frequent that an operator will operate a drill in one direction of rotation and then reverse the direction repeatedly especially when a hard rock condition is encountered. An object and feature of the present invention is the provision of a drive and joint connector which will provide axial engagement in either direction of rotation. Accordingly, the drill assembly may be placed under withdrawal tension when rotating in either direction.
A further object is the provision of a drill steel drive and assembly in which the parts are readily manufactured by conventional screw machines or forgings.
Other objects and features of the invention will be apparent in the following description and claims in which the invention is described together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.